Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/18/23
AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
857 PM CDT Mon Apr 17 2023
.UPDATE...
Issued at 854 PM CDT Mon Apr 17 2023
Nothing to update at this time of the night.
UPDATE Issued at 624 PM CDT Mon Apr 17 2023
Only adjusted the timing of the patchy fog in the James River
Valley as the RAP has some fog between 9-11z. Confidence is low in
the fog however.
&&
.SHORT TERM...(This Evening through Tuesday)
Issued at 247 PM CDT Mon Apr 17 2023
Current surface analysis places low over the Great Lakes into
eastern Ontario, with ridge stretching through the eastern plains.
Upper level analysis places low off the northwest Pacific coast,
with ridge over the northern plains. Over our area, rather quiet
weather remains, with a southeasterly breeze to the east of the
surface ridge over western parts of our area.
For tonight, a weak initial short wave slides mainly over western
portions of the area as upper ridge does a gradual progression
east. This may bring a little light rain over western areas.
On Tuesday, upper ridge continues to scoot over to the east as a
stout short wave swinging around the base of the Pacific ridge
works its way towards the Rockies. Elongated surface lee trough
deepens, resulting in breezy southeasterly winds over the area.
Precipitation chances from earlier mentioned initial wave lift
north, but chances with the second more stout wave will be
increasing in the afternoon.
.LONG TERM...(Tuesday Night through Monday)
Issued at 247 PM CDT Mon Apr 17 2023
As we go through Tuesday night, short wave starts to close off
over eastern Montana, while surface low lifts and deepens along
the Montana/North Dakota border. Precipitation spreads over the
area, with snow developing over the far north, mainly rain
elsewhere. Over southern locations, some instability is noted
which may lead to a few claps of thunder.
As we go through Wednesday, surface low lifts north/northeast
with the system, then stack up and lingers over north central
North Dakota. This will lead to winds becoming westerly over the
southwest, becoming quite gusty. Precipitation starts to wane
over the south with the lifting system, but continues over the
north. Where this becomes a bit concerning is primarily over the
far northwest where cold air gets wrapped into the system, and
snow continues, while further east/south more of a mix is
expected through the day before transitioning overnight while
chances stat to wane. NBM probabilities have increased a fair
amount for the possibility of over 6 inches along and north of
Highway 2 (~50-75%), though this includes going into Thursday.
There are some concerns on the potential impact with this as we
are in the time of year where insolation is similar to that of
later August, so when snow rates are lower, expect melting on
roadways. Either way, roads may be quite crummy overnight given
freezing temperatures.
On Thursday, greatest chances spread again through the north
while upper low starts to drop east-southeast, then eventually
makes its exit though chances do linger through Friday. Drier
conditions expected for the weekend, though temperatures will be
cooler.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 624 PM CDT Mon Apr 17 2023
VFR through the period with chances of rain across the north
starting overnight and breezy southeast winds at 30 knots through
Tuesday. Low confidence in fog at KJMS so left it out for now.
Clouds will move in overnight.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Smith
SHORT TERM...JJS
LONG TERM...JJS
AVIATION...Smith
Area Forecast Discussion
National Weather Service Pendleton OR
834 PM PDT Mon Apr 17 2023
.UPDATE...Current radar and infrared satellite imagery showing
light to moderate returns along the Blue Mountain Foothills and
extending east into the Lower Columbia Basin under mostly cloudy
skies. These returns are associated with isolated storm cells that
have been developing through this afternoon and are continuing
into the evening hours. Spotter reports and observations have
indicated that pea size hail and wind gusts of up to 40 mph have
occurred within this afternoon`s storm cells. However, storm
intensity will be waning through the remainder of the evening with
the lack of daytime heating. Showers are still expected along the
Blue Mountains/foothills and east overnight before lingering over
higher elevations of the Cascades, Blue, and Eastern Mountains
into Tuesday morning. Increased PoPs and QPF over areas of the
Lower Columbia Basin and Blue Mountain Foothills to better account
for developing showers and isolated storms with this evening`s
forecast update, along with minor edits to sky cover,
temperatures, and winds to better align with current observations
and recent guidance. Current highlights do look to verify as over
5 inches is expected along the east slopes of the Oregon Cascades
above 4500 feet, and overnight low temperatures are likely to
reach near 27 degrees in the Yakima and Kittitas Valleys. 75
&&
.PREV DISCUSSION... /issued 448 PM PDT Mon Apr 17 2023/
..Updated Aviation Discussion...
SHORT TERM...Today through Wednesday...An offshore low centered off
the BC coast will circulate rounds of precip into the forecast area
over the next several days, as well as drive unseasonably cool
temperatures through much of the work week. For today, a frontal
boundary associated with this low is beginning to push through the
Cascades, with a combination of SW flow aloft and upslope flow
beginning to spawn scattered showers ahead of the front. While
instability will be limited due to the cooler-than-average
conditions we`ve experienced since yesterday, both the synoptic
setup and convective parameters support a few isolated
thunderstorms, primarily across the mountains of central OR into the
eastern mountains. Most recent CAMs have backed off a tad on
depicting more organized convective cells across the eastern half of
the CWA, with the offshore low beginning to develop enough of a
negative tilt to push the main front more north and east of us, but
could still see convection and a few rumbles a thunder across the
foothills of the Blues into the mountains themselves, even where
snow levels are low enough to support snow. Orographic lift,
combined with a well-saturated environment and strong lapse rates,
should be enough to overcome these relatively cool temperatures for
thunderstorms. As far as mountain snow is concerned, the threat will
be primarily limited to the OR Cascades, where snow levels are low
enough to support accumulating snow at the pass level. A Winter
Weather Advisory is in effect for this area through Tuesday morning,
highlighting primarily the Santiam Pass area for any evening and
early morning commuters. A few inches of snow may also occur in the
Blues above 4000 ft.
Precip threat largely diminishes by daybreak Tuesday, as the upper-
level flow pattern becomes more zonal, allowing drier conditions to
prevail. Such a pattern would support only some light isolated
shower activity across our high mountains. Precip threat re-emerges
on Wednesday as the aforementioned low circulates another wave
through the interior Northwest. This weaker system will lead to a
more diminished threat across our lower elevations, with models
pinpointing primarily our mountain zones once again for precip
Wednesday. Snow levels look to be around 2000-3000 ft. Instability
doesn`t look to be as strong as Monday`s setup, but NAM and RAP do
key in on some low MUCAPE over the eastern mountains. As of now, any
activity looks again to be isolated in nature.
Freeze warnings continue for the Yakima and Kittitas Valleys due to
this offshore low allowing colder, northerly air to filter in.
Expect lows to dip into the upper 20s both Tuesday and Wednesday
morning for these areas, especially as the bulk of moisture
transport from this system falls to the areas` south and east. Highs
will remain primarily in the upper 40s into 50s across our
population centers through the short term period. Evans/74
LONG TERM...Thursday through Monday night...The long term will be
characterized by a bit of unsettled weather followed by drier
conditions through the weekend ahead of another system. Mountain
snow will start the long term followed by rain. Temperatures will
begin on the cooler side before returning to near normal over the
weekend.
Models are in slight agreement with the trough over the area before
departing by Thursday night. The most active day of the long term so
far will be Thursday with the chances of mountain snow being the
highest. With that said, the NBM probabilities of snow over the Wa
Cascades is 89%, Or Cascades is 99% and the Blue mountains is 50%
for 1 inch of snow Thursday. Snow levels on Thursday will begin
around 1200ft before rising to near 4000ft. EFI does show that much
of the region will still be under the seasonal average with
temperatures in the low 60s across the Basin, 50s in the Gorge,
Kittitas/Yakima Valleys, Central Or and the foothills of the Blues
and in the 40s elsewhere.
Friday through Saturday night the models are in slight agreement
with the incoming ridge. All models show the ridge coming in Friday
and remaining through Saturday night with variances in the amplitude
and timing. GFS has the ridge breaking down and becoming more zonal
as the next trough moves in from the BC coast, ECMWF and Canadian
models show the ridge remaining but more to the east. All show some
precipitation beginning to move in ahead of the trough. EFI shows
that Friday through Sunday will begin to hedge towards normal
temperatures each day with highs in the mid 60s in the Basin,
Yakima Valley, Gorge and along the foothills of the Blues, 50s in
Central Or and Kittitas Valley and elsewhere in the 40s.
Temperatures will steadily increase each day with Sunday being the
warmest day of the period with temperatures nudging the high 60s and
70s in the Gorge, foothills of the Blues, Basin and adjacent
Valleys, Central Or and the adjacent Valleys with high 40s to low
50s elsewhere.
The models begin to truly diverge by Sunday into Monday with very
little agreement. All models are showing different outcomes and
clusters are all over the place. For now have just continued with
the NBM guidance for the end of the forecast period which has
precipitation returning to the forecast area Sunday morning across
the mountains before sweeping across the region through Monday.
Bennese/90
AVIATION...00Z TAFs...VFR conditions currently observed at all
sites, which will stay the course through the period. Showers are
expected for PDT/ALW through the evening before drier conditions
ensue by 07Z. Winds will stay breezy with gusts of 20-30kts out of
the southwest for all sites, with the exception of DLS which winds
will stay below 10kts through Tuesday afternoon. Wind gust
observations are already above 20kts for RDM/BDN/PDT, with ALW/PSC
joining after 06Z and YKM early Tuesday morning. 75
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 34 51 33 51 / 70 10 10 30
ALW 37 54 36 54 / 80 10 10 50
PSC 39 57 38 58 / 50 0 0 10
YKM 29 53 30 54 / 30 10 0 10
HRI 35 56 35 57 / 50 10 0 10
ELN 29 49 30 50 / 40 10 0 10
RDM 26 45 28 44 / 20 10 10 20
LGD 30 43 28 44 / 80 30 10 70
GCD 27 43 28 44 / 80 20 10 60
DLS 34 55 36 54 / 20 20 20 20
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 5 AM PDT Tuesday for ORZ509.
WA...Freeze Warning from 2 AM to 9 AM PDT Tuesday for WAZ026-027.
Freeze Warning from 2 AM to 9 AM PDT Wednesday for WAZ026-027.
&&
$$
SHORT TERM...75
LONG TERM....90
AVIATION...75